The present invention relates to a television camera and, more particularly, to a television camera having an automatic focusing device for an electron beam of a pickup tube.
In general, for the purpose of focusing an electron beam in a pickup tube of a television camera a test chart called "resolution chart" or a registration chart is used. The registration chart is used to minimize the registration error of a color television camera, and has a chart depicted thereon which may be used in focus adjustment. The focus adjustment is achieved by visually observing with a monitor a video signal obtained by picking up the abovementioned chart and by regulating a focusing current flowing through a focusing coil in case of an electromagnetic focusing type pickup tube and a voltage of a focusing electrode in case of an electrostatic focusing type pickup tube. It is necessary to adjust an electron beam for each pickup tube in case of a color television camera using a plurality of pickup tubes. The above-described conventional electron beam focus adjusting method is feasibly affected by the skilfulness and subjectivity of a camera technician. Accordingly, uniform quality of a picture can hardly be obtained among the pickup tubes. Further, a plurality of television cameras are simultaneously used generally in a television broadcasting station. In order to equalize the picture equality or cameras, only sole camera technician adjusts a plurality of television cameras, and it accordingly takes a long time for the focus adjustment of electron beams.